Liquid crystal display devices are widely applied in many electrical devices, for example, monitors, television sets, and mobile phones. The liquid crystal display devices apply liquid crystal capacitors constituted by pixel electrodes, common electrodes, and liquid crystal layers to maintain an electrical field to rotate the liquid crystal molecules and control the passing of light to display images. However, when the liquid display devices transfer from a frame of image to another frame of image, common voltages applied to the common electrodes are easily affected by the capacitors' coupling signals, such that crosstalk is generated. To solve the crosstalk problem, feedback circuits are generally applied to detect the common voltages and generate feedback signals.
The feedback circuits are generally positioned on flexible printed circuit boards. The flexible printed circuit boards are independently positioned outside substrates of the liquid crystal display devices. The flexible printed circuit boards include signal processing circuits. The signal processing circuits amplify the feedback signals and reduce the noise of the feedback signals and then transmit the processed feedback signals back to display drive circuits of the liquid crystal display devices. The display drive circuits adjust electrical potentials of the common electrodes, so as to improve the quality of the images.